1. Field of the Invention
The present invention relates to a frame transfer prober for performing electrical property tests on a number of semiconductor chips fixed to a dicing tape and, more particularly, to a frame transfer prober which can detect the separation of a semiconductor chip from the dicing tape.
2. Description of the Related Art
A number of semiconductor devices having the same electric device circuit formed thereon are formed on a surface of a wafer and, in order to test the electrical properties of each electric device circuit before the electric device circuits are cut into individual semiconductor devices (semiconductor chips), the electric device circuits are tested by a prober to see whether they are good or not good. In general, the prober has a probing needle which corresponds to each semiconductor device on the wafer and is constructed such that a probe card connected to a tester is made to correspond to each semiconductor device on the wafer sequentially so that the probing needle is brought into contact with an electrode pad of the semiconductor device to thereby implement an electrical measurement.
In recent years, in order to realize a miniaturization in size, weight and thickness of electronic apparatuses such as mobile phones, digital cameras and portable information terminals, the installation techniques for semiconductor integrated circuits have entered the stage of chip size package (CSP) or wafer level chip size package (WCSP). In a CSP, semiconductor chips are stacked for use.
Due to this, wafers have been in demand which are thinned to 100 μm or smaller and, in wafers which are so thinned, the occurrence of failure becomes highly probable while the wafer is cut into individual semiconductor chips in a dicing process that is carried out after the electrical property test has been performed on the semiconductor chips by the prober. In addition, it has been desired to reduce the defective fraction of actually installed semiconductor chips by performing the electrical property test at as late a stage as possible where processed semiconductor devices are close to being final semiconductor chip products.
It is conventional practice to perform the electrical property test on semiconductor chips using a frame transfer prober. In this case, in order to prevent individual semiconductor chips which are cut in the dicing process from scattering, the wafer is diced after a dicing tape has been applied to a surface of the wafer where the number of semiconductor devices are not formed. The dicing tape is formed into a circular shape which is similar to the shape of the wafer, and the dicing tape is extended to increase the diameter thereof after the wafer has been diced and is then held in the extended state by a ring-shaped metallic frame. Namely, individual semiconductor chips so produced are held while being affixed to the dicing tape in a state where intervals (cuts) between the individual semiconductor chips are slightly expanded. The semiconductor chips are transferred in that state on a frame, and the electric property test is performed on each semiconductor chip while the semiconductor chips are held on a stage of a frame transfer prober.
In the conventional method, however, there sometimes occurs a case where a semiconductor chip is separated from the dicing tape. In the event that the electric property test is performed in this state, there has been caused a problem that the semiconductor chip that is separated is brought into contact with a probe card needle of the frame transfer prober, whereby the probing needle and the chip are damaged, or the separated semiconductor chip collides against an alignment camera when aligning the chip for positioning, whereby the alignment camera and the chip are damaged.